So what exactly is the difference between readdir and print? They're both built in functions. You hit the nail on the head with the last paragraph. If you don't trust parts of the language to work, how can you trust any of it?
I think you can do that. For instance, some earlier implementations of threads in Perl were... a bit unstable. You could distrust those, without avoiding the language altogether.
Of course this is a dramatically extreme case: he doesn't trust a demonstrably stable part of the system, so that's a bit different.